Is it possible to put an image on a liquid body?
You can use a UV project modifier. It can make an empty act as projector to beam an image onto an object.

This does the same thing as going into Edit Mode, looking at your object from above and choose Unwrap -&gt; From View. However it does work with objects that don't even have/support a UV map.
EDIT: If you are not dead set on using a fluid animation, I would suggest Dynamic Paint waves. You can combine brushes that paint maps (as mask for your image) and a different brush to make waves. For further information I'd need a reference of what you are trying to achieve.
Also: You can try using a shrinkwrap modifier on a UV-Unwrapped plane that follows your fluid surface.